1. Field of the Invention
The present invention is related to an image sensing module, and more particularly to a contact image sensing module with a movement detecting function.
2. Description of Related Art
An image sensing module uses an optical technique to draw an image of a sensed object. For example, an image sensing module with a fingerprint scanning function is used to draw a planar image. The image sensing module must therefore be able to detect a moving speed of the fingerprint on the module to obtain fragmental fingerprint images. A complete fingerprint image can thus be integrated by means of operation processing.
A conventional image sending module with a movement detecting function, such as “Method and apparatus for scanning a fingerprint using a linear sensing” disclosed in TW 544630 published on Aug. 1, 2003, includes a linear image device, a roller, a light source, a focusing device, and rotatable detector. The roller is used to provide a fingerprint to be moved thereon. The light from the light source is transmitted to the roller, reflected by the fingerprint to the focusing device and focused on the linear image device. The rotatable detector is used to detect the rotation speed of the roller for obtaining the moving speed of the fingerprint.
The above conventional image sensing module with a movement detecting function needs the roller and the rotatable detector to decide the moving speed of the fingerprint. As a result, the whole image sensing module is large and complex in structure. It is not suitable for assembly on a microminiaturized electronic apparatus.
Moreover, for accurately transmitting the light to the linear image device, the position of the focusing device cannot have any deviation. Therefore, the small tolerance may lead to a high quality assembling demand so as to influence the product yield.
Furthermore, the non-uniform light magnitude transmitted from the light source to the roller may result in a complex operation processing of the drawn fingerprint image by the conventional image sensing module and therefore a low efficiency.
In addition, if the number of light sources, which are alternatingly arranged under the roller, is increased, the problem of a non-uniform light magnitude may still exist, and the cost and the power consumption may also be increased as well.